I've read your other posts; what a dilemma for sure. I could only hope that my husband would go to the lengths that you have been going to in making a most difficult decision.
Your therapist sounds like she is using a form of cognitive therapy. And, it would be VERY wise to follow her suggestions to get out by yourself. A person in your situation is at real risk for depression. Your sense of self and your feelings become more and more dependent on someone elses. Your choices seem more and more limited to the situation that you are already in.
Everyone, even if they don't have a spouse with a disease, needs to be a whole person apart from the person they married. It's harder when you are trying to meet increased needs of a spouse, but as I mentioned earlier, if you don't carve out a part of life that is yours (while still acknowledging your spouses life and your life as a couple) it can be dangerous for YOUR emotional and even physical self.
You can't be of any help to her OR your relationship if you don't make time for yourself!
Maybe all of us here on the Boards are a good kind of therapy too?